1. Field of the Invention
The present invention relates in general to a computer system, and more particularly to a serial port switching circuit for selectively connecting two serial ports of an input/output controller to two serial communication connectors which are connected to external equipment, to allow the input/output controller to perform serial data communication with the external equipment.
2. Description of the Prior Art
In general, a computer system includes a central processing unit for controlling the entire operation of the computer system, a read only memory for storing an operating program of the central processing unit therein and a random access memory for storing work data of the central processing unit therein.
A display controller connected to a display is also provided for displaying the operation status of the computer system under the control of the central processing unit.
An input/output controller for performing data communication with external peripheral equipment and other computer systems is also provided.
The central processing unit, read only memory, random access memory, display controller and input/output controller are normally interconnected via a bus.
A keyboard, auxiliary storage units, such as a hard disk drive, a floppy disk drive, etc., are connected to the input/output controller as are parallel and serial ports which are connected to various peripheral equipment such as a printer, a mouse, etc., for performing data communication.
The input/output controller is generally provided with two serial ports which are connected to two serial communication connectors, one having twenty-five pins and a second having nine pins.
For the purpose of switching the connections between the first and second serial connectors and the first and second serial ports of the input/output controller, the user must directly physically switch the cable connections or adjust the addresses of the first and second serial ports of the input/output controller when it is necessary to reverse the connections between the first and second serial ports of the input/output controller and the first and second serial connectors.
As result, much time is required in switching the connections and such switching is very inconvenient.
The following patents each disclose features in common with the present invention but do not teach or suggest the specifically recited circuit for selectively connecting two serial ports of an input/output controller to two serial communication connectors as recited by the present invention.
U.S. Pat. No. 5,247,682 to Kondou et al., entitled System And Method For The Automatic Setting Of A Computer System's I/O Configiuration, U.S. Pat. No. 5,471,585 to Barakat et al, entitled Personal Computer System With Input/Output Controller Having Serial/Parallel Ports And A Feedback Line Indicating Readiness Of The Ports, and U.S. Pat. No. 5,355,507 to Nishikawa, entitled Computer System For Arbitrating The Operation Of A Built-In Modem And External SIO Circuit.